Crystallization of kesterite Cu2ZnSnS4 prepared by the sulfurization of sputtered Cu–Zn–Sn precursors

Abstract The one step deposition of a single layer of a Cu–Zn–Sn (CZT) precursor by radio frequency magnetron sputtering from an alloy target was performed to prepare kesterite Cu2ZnSnS4 thin film compound. The crystallization of Cu2ZnSnS4 after sulfurization at elevated temperatures was studied. Chemical reactions at 250 °C to 350 °C resulted in the formation of binary sulfides (CuS, SnS and ZnS), as well as a ternary sulfide (Cu2SnS3). Subsequently, the crystallization of kesterite Cu2ZnSnS4 was achieved from a reaction between ZnS and Cu2SnS3 at temperatures ranging from 400 to 550 °C. At 400 °C, Cu2ZnSnS4 was formed in the presence of secondary phases. These secondary phases disappeared gradually as the temperature was increased with a single Cu2ZnSnS4 phase observed at 500 °C and above. The optical properties of Cu2ZnSnS4 films were characterized and the direct energy band gap for Cu2ZnSnS4 films was estimated to be 1.51 eV.